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Date: Thu, 30 May 2024 14:08:59 -0700
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH net-next v6 1/3] net/mlx4: Track RX allocation failures in
 a stat
To: Joe Damato <jdamato@fastly.com>, <linux-kernel@vger.kernel.org>,
	<netdev@vger.kernel.org>
CC: <nalramli@fastly.com>, <mkarsten@uwaterloo.ca>, Tariq Toukan
	<tariqt@nvidia.com>, "David S. Miller" <davem@davemloft.net>, Eric Dumazet
	<edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni
	<pabeni@redhat.com>, "open list:MELLANOX MLX4 core VPI driver"
	<linux-rdma@vger.kernel.org>
References: <20240528181139.515070-1-jdamato@fastly.com>
 <20240528181139.515070-2-jdamato@fastly.com>
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From: Jacob Keller <jacob.e.keller@intel.com>
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On 5/28/2024 11:11 AM, Joe Damato wrote:
> mlx4_en_alloc_frags currently returns -ENOMEM when mlx4_alloc_page
> fails but does not increment a stat field when this occurs.
> 
> A new field called alloc_fail has been added to struct mlx4_en_rx_ring
> which is now incremented in mlx4_en_rx_ring when -ENOMEM occurs.
> 
> Signed-off-by: Joe Damato <jdamato@fastly.com>
> Tested-by: Martin Karsten <mkarsten@uwaterloo.ca>
> Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
> ---
>  drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 1 +
>  drivers/net/ethernet/mellanox/mlx4/en_rx.c     | 4 +++-
>  drivers/net/ethernet/mellanox/mlx4/mlx4_en.h   | 1 +
>  3 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> index 4c089cfa027a..4d2f8c458346 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> @@ -2073,6 +2073,7 @@ static void mlx4_en_clear_stats(struct net_device *dev)
>  		priv->rx_ring[i]->csum_ok = 0;
>  		priv->rx_ring[i]->csum_none = 0;
>  		priv->rx_ring[i]->csum_complete = 0;
> +		priv->rx_ring[i]->alloc_fail = 0;
>  	}
>  }
>  
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> index 8328df8645d5..15c57e9517e9 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> @@ -82,8 +82,10 @@ static int mlx4_en_alloc_frags(struct mlx4_en_priv *priv,
>  
>  	for (i = 0; i < priv->num_frags; i++, frags++) {
>  		if (!frags->page) {
> -			if (mlx4_alloc_page(priv, frags, gfp))
> +			if (mlx4_alloc_page(priv, frags, gfp)) {
> +				ring->alloc_fail++;
>  				return -ENOMEM;
> +			}
>  			ring->rx_alloc_pages++;
>  		}
>  		rx_desc->data[i].addr = cpu_to_be64(frags->dma +
> diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> index efe3f97b874f..cd70df22724b 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> +++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> @@ -355,6 +355,7 @@ struct mlx4_en_rx_ring {
>  	unsigned long xdp_tx;
>  	unsigned long xdp_tx_full;
>  	unsigned long dropped;
> +	unsigned long alloc_fail;
>  	int hwtstamp_rx_filter;
>  	cpumask_var_t affinity_mask;
>  	struct xdp_rxq_info xdp_rxq;

This patch does not appear to extend either a netdev, ethtool, devlink,
or any other interface to report this new counter.

How is a user supposed to obtain this information from the driver?